This invention relates to mats suitable for use as battery separators and, more particularly, to such mats with degradation resistant spacer embossments formed therein.
Producing battery separators that have a long life in the rigorous environment of a lead acid storage battery has long presented a multitude of problems. Progress toward the solution of these problems is well recorded in the patent literature. A minor failure in the separator can result in the loss of the complete useful life of a battery. When areas of a separator are embossed to provide for a spacing function, these areas are particularly susceptible to failure because they receive a greater abuse from scouring and buffeting as a result of the vibration and shifting of the battery parts per unit area. This is because of the smaller area in contact with the battery plate. In addition, the embossments are normally engaged against the positive plate where the conditions condusive to the highest oxidation rate are present.
For these and other reasons the formation of spacer areas in battery separators that differ from the adjacent areas is known as shown in U.S. Pat. Nos. 1,357,378; 2,626,429; 2,687,445; 2,687,446; and 2,850,559. It is also known to protect felted fibers from the acid environment of a battery by, for example, coating the web as shown in U.S. Pat. No. 2,687,447.